JP-A-H5-106427 published by the Japan Patent Office in 1993 discloses a filter for an engine exhaust gas system to purify particulate matter (hereafter, referred to as “exhaust gas particulates”) discharged from an engine such as a diesel engine. The filter is regenerated by oxidizing or burning the trapped exhaust gas particulates at a predetermined interval. Regeneration of the filter is performed by raising the exhaust gas temperature. The increase of exhaust gas temperature is achieved by engine control, such as applying an angle retardation to the fuel injection timing or performing a secondary injection in addition to the main injection.
The temperature of the filter surface on which particulates are deposited is referred to as “bed temperature”. The bed temperature of the filter is computed based on the exhaust gas temperature on the filter inlet side and outlet side. The engine control is performed so that this bed temperature becomes a targeted value. In this way, exhaust gas particulates can be burned efficiently.